I'm surprised your system boots at all. Perhaps it's not using the boot partition. I suggest you review How to Resize LVM Root in Oracle Linux 7 to backup you server as outlined, including the boot partition, and then remove the boot partition from your LVM setup and restore the data.

Having a /boot partition is not essential. GRUB2 is able to understand many filesystem layouts. If you are configured to use a boot partition pathnames in /boot/grub2/grub.cfg are relative to the boot partition:

linux16 /vmlinuz-0-rescue-b016b1c73e7043ad8f69fe963a13fe66 root=

but if a boot partition is not used, the filenames are relative to the root filesystem:

linux16 /boot/vmlinuz-0-rescue-b016b1c73e7043ad8f69fe963a13fe66 root=

A 500MB /boot partition should be enough unless /etc/yum.conf is configured to keep lots of install-only packages:

# installonly_limit=3installonly_limit=300

and I certainly do not recommend doing that. All most people need is a current kernel and the last working kernel for fallback.

Grub replaces the Master Boot Record (512 bytes) at sector 0 to execute the GRUB bootloader. Are you sure /boot is not required for GRUB? If I remember correctly, LILO did not use /boot, but GRUB requires files in /boot, but it does not have to be on a separate partition.

The reason for the /boot partition are, or used to be many years ago:

a) If the BIOS isn't int13h extended, it can only read the first 8 GB of a disk.

Although LVM should be supported according to the the grub2 manual, specifying LVM for the /boot partition fails using the OS installer (7.6), showing the following error that /boot file system cannot be type lvmlv.